It is well-known to mount a timber-working head in the form of a harvesting head to a carrier to perform a number of functions in connection with timber. For example, the head may be used to grapple and fell a standing tree and process the felled tree by delimbing, possibly debarking (depending on the configuration of the head), and cutting a trunk of the tree into logs (e.g., logs of predetermined length). Processing the felled tree typically involves feeding the felled tree in axially opposite directions, as needed, along a feed axis while grappling the tree.
The feed mechanism of the head may take a variety of forms. For example, as with the well-known Waratah HTH624C, the feed mechanism may have two arm-mounted drives and a frame-mounted drive synchronized with the arm-mounted drives. Each arm-mounted drive has a feed wheel mounted at the end of a respective feed arm pivotal relative to the frame and operable by a hydraulic motor of the arm-mounted drive.
The frame-mounted drive has a feed wheel mounted in a cavity of the frame and operable by two hydraulic motors of the frame-mounted drive each of which is bolted to the frame and arranged in flow-series with the motor of a respective arm-mounted drive. Each motor of the frame-mounted drive comprises a rotary output element in the form of an externally splined shaft received in an internally splined center hub bolted to the feed wheel for rotation of the feed wheel, center hub, and shafts about a rotation axis. As such, the rotational speed of the feed wheels of the arm-mounted and frame-mounted feed wheels is synchronized, irrespective of torque demand.
The assembly process of the frame-mounted drive is somewhat involved. It includes bolting the center hub to the feed wheel and inserting the center hub/feed wheel assembly into a cavity of the frame. Both sides of the internal spline of the center hub are greased. A first of the motors of the frame-mounted drive is fitted into the frame, the shaft of the first motor and the center hub are connected via the splines thereof, and the first motor is then bolted to the frame. The second motor of the frame-mounted drive is fitted into the frame with a standard shim set between the second motor and the frame, the shaft of the second motor and the center hub are connected via the splines thereof, and the second motor is then bolted to the frame. A dial gauge is used to measure the float of the center hub/feed wheel assembly on the motor shafts axially along the rotation axis. The second motor is unbolted, and the amount of shims required to eliminate such axial float and apply approximately 0.005 inch compression on the seals located between the center hub and the motor housings is removed. The first motor, with the correct number of shim(s), is re-assembled into the frame, to complete assembly of the frame-mounted drive.
Regarding maintenance, the splined connected between the internally splined center hub and the externally splined motor shafts needs to be greased periodically (e.g., every 200-250 hours of operation in hardwood applications and every 1000 hours of operation in softwood applications). To do so, a technician typically enters a caution zone (located between the feed arms) to access the frame-mounted drive, and disassembles the center hub/feed wheel assembly from the motor shafts to re-grease both ends of the center hub. The frame-mounted drive, with its re-greased center hub/feed wheel assembly, is then re-assembled.